Hudson Valley Experience with Nut Tree Understocks
Reading edition
Gilbert L. Smith, Millerton, N. Y.
This report is not based on any planned or well conducted experiments, but is based simply on our observations of results of our grafting work over the years since 1934.
Our first work was with hickories, so I will start with them.
Our first year's grafting was done in a plot of practically pure pignut stocks. This was the seven leaflet pignut, which I believe to be Carya glabra. I have never been sure of the identification of the two species of pignuts. We secured a fairly good percentage of living grafts, which grew well the first summer. The next spring all of the grafts failed to leaf out and later were found to be dead. A few grafts which were put on bitternut stocks (Carya cordiformis) grew well, and are still growing well after more than fifteen years. Several different varieties of shagbark hickory scions were used in this grafting.
The second year, we again grafted as many or more stocks in this same area. The results were exactly the same, except that we used some scions of Davis and Fox. (These varieties were brought to light through the contests of the previous winter). The grafts of Davis grew on pignut stocks, are still alive and doing fairly well. They have been bearing for several years, although the squirrels have stolen all of the nuts. Grafts of all other varieties which were on the pignut stocks died the next spring. One graft of Fox on mockernut lived and has continued to grow fairly well. That same year we started our test orchard of shagbark stocks (Carya ovata) in a different area. Grafts on these stocks have grown very well.
I believe that for some reason grafts of shagbark on pignut stocks cannot stand cold weather. Certainly, incompatibility is very marked.
Our experience with hickory stocks to date is as follows:
Pignut (Carya glabra or possibly Carya ovalis). This species is worthless as a stock for shagbark, shellbark, and hybrids of these species. If nut growers have some pignut stocks growing where they especially wish to have some good hickory trees, they can graft them to Davis. We have also heard that Brooks will grow on pignut stocks.
Mockernut (Carya alba). This species is also nearly worthless as a stock for shagbark, shell bark, and hybrids, although many more varieties will live on it than will on pignut stocks.
Shagbark (Carya ovata). This species makes the most dependable stock of any we have tried so far, for shagbark, shell bark, and the hybrids. Its greatest drawback is the long time it takes to grow seedlings to a size large enough to graft.
Shellbark (Carya laciniosa). We have never had an opportunity to use this species as a stock. I think that it would make a good one and possibly be faster growing than shagbark.
Bitternut (Carya cordiformis). We have found that this species makes a very satisfactory stock for shagbark and hybrid grafts. We have not tried shellbark on it, except Berger which grows well on it. Seedlings of this species are much faster growing than are shagbark seedlings, and thus are large enough to graft sooner. We have grafts growing on bitternut stocks since 1935, they are growing and producing well. We consider this species as good or nearly as good as shagbark as a stock.
We have received contrary reports from farther south. These may be due to stock being blamed for something they did not cause or it may be that bitternut stocks grown from seed of more southern origin may not be as good as our northern stock.[18]
Pecan (Carya pecan). Our experience with this species as a stock is very limited and has been confined to grafts of only one variety of shagbark (Wilcox). Results were very disappointing, but we have been told by others that it makes a good stock. It is much faster growing than is shagbark.
Walnut
In walnut grafting, we have found that the eastern black walnut stocks are so much superior to any others we have been able to find, that we have discarded all others.
Butternut (Juglans cinerea). We have found that it is much harder to secure living grafts on this stock than on black walnut. It also attracts butternut curculio to the nursery.
Japanese Walnut (Juglans sieboldiana and variety cordiformis). We have found that seedlings grown from either of these species are a great attraction to the butternut curculio. They are more difficult to secure living grafts on, and grafts on these stocks are very definitely less hardy than similar grafts on black walnut growing side by side. We have proved this repeatedly.
Persian Walnut (Juglans regia). We have never used this species as a stock, and in view of the fact that grafts of it grow so well on black walnut stocks, I can see no use in even trying it.
Eastern Black Walnut (Juglans nigra). As stated above, we have found this to be the ideal stock for all walnut grafting. It is more free from insects than any of the other walnuts. Grafts grow well on it and are more hardy than grafts on some of the others.
We have not had enough experience in grafting chestnuts and filberts even to offer any comment as to stocks for them.